howardt

Three times on my 07 HHR the ignition key would not turn on initial try. After many tries, it would return to normal for 5 to 6 weeks. Replaced the ignition cylinder from a diagnosis of sticking tumblers, swithches OK. I'm curios though about the key itself. How is the car recognizing that the correct key is in the ignition even when all the tumblers are actuated correctly ??

firemangeorge

The key has a "chip" in it designated by a + symbol stamped on the key. The key not being able to turn in the ignition is usually a tumbler problem.
Two seperate things here.
Key turns in the ignition but doesn't start. Possibly the key needs programming or you have a non chip key.
Key won't turn in the ignition. Possible tumbler bad, worn key, wrong key.

There are other possibles like shifter, linkage, bad ignition switch etc., but yours sounds to be key/tumbler problem.

donbrew

The chip in the key is read by a chip in the steering column. The tumbler & key teeth have nothing to do with the CAR recognizing the key. I am assuming that you either had a pro do the work or you did the "new key matching" procedure.

What about the door locks, if you got a new key/cylinder pair?

db/sb

If the person that did the work pinned the new ignition cylinder to the existing key, nothing would change as far as the door lock (there's only one) is concerned.

donbrew

That's what I meant by a pro doing the work.